1. Field of the Invention
This disclosure concerns animal cage box enclosures and the fittings by which utility connections are made into the interior of the cage box, especially for passage of water lines for drip fittings. A lightweight cage box is provided and is disposable, whereas a grommet for receiving a water fitting can be removed and reused.
2. Prior Art
High density animal caging systems are used in laboratories and other applications, wherein plastic boxes form cages that confine one or more animals, such as laboratory mice, rats, etc. A number of such cages can be kept in shelving that optionally has conduits for bringing ventilation and drinking water to each box. Caging systems of this type are available from Thoren Caging Systems, Inc. of Hazleton, Pa. and are exemplified by U.S. Pat. Nos. 5,474,024; 5,044,316; and 4,690,100.
The cages typically comprise a rigid one-piece injection molded clear polycarbonate box with an open top. In some exemplary embodiments, the box may be flanged for hanging the cage under one or more ventilation conduits. The box may receive a wire rack with a receptacle for food pellets or a water bottle. A filter cover may fit over the top to prevent passage of dust and dander. The animals can be observed through transparent side walls. In order to care for the animals, for example to change the bedding, the cage boxes are withdrawn from the shelving. In the case of water and ventilation lines brought to the cage by the shelving, withdrawing the cage box from the shelving also disengages the cage from water and air supplies.
More or less complicated structures are provided in the wall of the cage box wherein the water or air supply conduit attaches to the cage or extends through the cage wall. Examples of such structures include inwardly or outwardly opening cup shapes with flanges overlapping the cage wall around an opening for a water or air line or fitting to pass through. Some variations comprise shapes that are molded into the side wall of the cage box, but typically, a round opening is provided in the cage wall and a fitting such as grommet is permanently affixed to the cage wall at the opening.
As used in this disclosure, the term “grommet” is used to refer to any of various protective or functional elements that line an opening through a wall, or carry a passageway through a wall between opposite sides, with one or more flanges or similar parts resting against at least one side of the wall to retain the grommet in place.
In the case of a plastic molded cage box, an inner or outer grommet part may have a flanged cylindrical tube, for example, fitted into a round opening in the cage wall such that the flange rests against the surface of the cage wall adjacent to the opening on a first side. A complementary opposed grommet washer or flange or similar part typically resides against the cage wall adjacent to the opening on the opposite side, causing the grommet or grommet assembly to be permanently captured at the opening. Typically, the cage wall is about 5 mm thick. The flanges surrounding the opening extend about 5 mm outwardly from the perimeter of the opening. The opposed part might be press fit over or into the tube or might be spot welded, threaded or similarly affixed. The opposed part has an annular flange or washer that engages against the cage wall on an opposite side.
In various embodiments, the grommet can carry part of the conduit or might carry a closure element such as a slotted rubber or plastic panel through which a tube is pushed. However in the case of animals such as mice, it is advisable to shield from animal access any parts that might be gnawed away. It is also advisable to provide parts that fit together without undue clearance. A mouse, and especially a mouse pup, can squeeze through a relatively small opening to escape. For these reasons, grommets typically are durable stainless steel elements, for example 18 or 20 gauge stainless steel stamped sheet metal forms. In an example provided in caging systems marketed by Thoren Caging Systems, Inc., a cover flap is mounted to hinge inwardly over a central hole when the cage is pushed into place on the shelf, i.e., when inward pressure from the water fitting during insertion presses the flap aside. The flap is spring biased to close the opening when the cage is pulled away from the water fitting, preventing the occupants from escaping through the opening.
The typical cage is a durable assembly wherein the cage box comprises a molded polycarbonate box with a permanently affixed stainless steel grommet. The cage box material is typically high temperature polycarbonate, as needed to survive handling, hot water washing with effective sanitizing chemicals and autoclaving to 135° C.
An inexpensive but less durable cage box is also known, but is intended to be disposable or at least less long-lived. This single use disposable cage box comprises a less durable material that is relatively thin and more flexible than a polycarbonate cage box, e.g., 1 mm thick polyethylene sulfonate. The disposable cage box is inexpensive, including when one factors in the fact that the disposable box need not be processed by autoclaving or the like. The disposable box has a sufficiently rigid edge flange to support a wire rack and a cage cover like a polycarbonate box.
The disposable cage box also could be outfitted with a grommet for receiving the input of a watering fitting provided in a shelf rack and placed to pass through the grommet when the cage is inserted into the shelf rack. A grommet or something functionally similar is necessary, namely to provide a route for the water fitting when inserted or retracted from the cage box, and a closure that reduces or eliminates clearance through which animals might escape, and either fits over or prevents access to edges of the passage through the cage box wall, where the animals would gnaw if given the opportunity. Unfortunately, however, a grommet structure sufficient to do the job is more expensive than the disposable cage box. As a result, disposable cage boxes are not used with push-in watering facilities.
What is needed is a way to exploit the cost savings of single use cage boxes that can be discarded after a single use, without adding the cost of a water-fitting grommet.